The present invention relates to a master link, of the type generally described in U.S. Pat. No. 3,659,112, that is usable in a track chain of the type generally described in U.S. Pat. No. 3,601,212. Such a track chain normally has a plurality of parallel shafts, each formed by a coaxial pin and bushing and linked together by pairs of links. A track shoe is secured to each pair of links between the respective shafts.
A master link is provided so that the endless track formed by an annular succession of such links can be opened for mounting on the respective guides and for servicing in general. It is critical that this master link be at least as strong as the other links of the chain.
Normally the master link comprises, like the rest of the chain, two axially spaced links between the respective shafts. Each of these links is, however, formed by two separate link parts that have axially engaging inner faces. The two links parts of each such link are secured axially together. In the older prior-art system this was done simply by bolting them together, forcing their faces into tight axial engagement with each other. This system was found largely deficient as the enormous forces urging the shafts radially apart were sufficient to shear the bolts in many cases.
Thus recourse was had to the system described in above-mentioned U.S. Pat. No. 3,659,112. The inner faces of the individual link parts are formed with interengaging teeth meshed with one another. At the same time the bolts are provided to axially secure each link part with the other respective link part. The use of such toothing thus greatly reduce the shear forces to which these bolts are subjected.
The specific disadvantage of such a system is, however, that if the attachment bolt loosens at all, as is frequently the case due to simple thermal expansion and contraction combined with the enormous load such links are subjected to, the radial forces between the respective shafts have to be taken up almost exclusively by the bolt. The result is, once again, subjecting the attachment bolt to considerable shear forces which can lead to sudden failure capable of producing a serious accident. Any in-the-field failure of such a track chain often entails considerable down time for a very expensive piece of equipment and requires extremely difficult on-the-job repairs.